Exposure apparatus and device manufacturing method

ABSTRACT

An exposure apparatus which exposes a substrate via a liquid, comprises: a projection optical system configured to project a pattern of a reticle onto the substrate; a substrate stage configured to hold the substrate and move; a top plate which is arranged on the substrate stage and in which an opening is formed; and a measurement member which is arranged in the opening formed in the top plate arranged on the substrate stage, wherein a gap is formed between the top plate and the measurement member in a plane perpendicular to an optical axis of the projection optical system, and wherein the measurement member is formed of one of a regular N-sided polygon (N&gt;4) and a circle in the plane.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 12/052,086 filed Mar. 20, 2008, which claims priority toJapanese Patent Application No. 2007-097629 filed Apr. 3, 2007, each ofwhich is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an exposure apparatus and a devicemanufacturing method.

2. Description of the Related Art

A process of manufacturing a micropatterned semiconductor device such asan LSI or VLSI adopts a reduction projection exposure apparatus whichreduces the pattern of an reticle and projects and transfers it onto asubstrate coated with a photosensitive agent. Along with an improvementin packaging density of semiconductor devices, further micropatterningis becoming necessary. The exposure apparatus has coped with themicropatterning along with the development of the resist process.

To improve the resolving power of the exposure apparatus, there are amethod of shortening the exposure wavelength and a method of increasingthe numerical aperture (NA) of a projection optical system.

To practice the method of shortening the exposure wavelength, variouslight sources are under development. That is, the exposure wavelength isshifting from the 365-nm i-line to a ArF excimer laser oscillationwavelength of about 193 nm. An exposure apparatus using the ExtremeUltra Violet beam (EUV beam) with a smaller wavelength of 10-15 nm thanultraviolet wavelength are also under development.

To practice the method of increasing the numerical aperture (NA) of aprojection optical system, a projection exposure technique using animmersion method is receiving a great deal of attention. The immersionmethod is used to perform projection exposure while the space betweenthe final surface of a projection optical system and the surface of asubstrate (e.g., a wafer) is filled with a liquid instead of a gas,unlike a conventional method. The immersion method has an advantage ofimproving the resolving power as compared with the conventional methodeven when a light source used has the same wavelength as that in theconventional method.

Assume that a liquid supplied to the space between a projection opticalsystem and a wafer is pure water (refractive index: 1.33), and themaximum incident angle of a light beam applied on the wafer in theimmersion method is equal to that in the conventional method. In thiscase, as the NA of the projection optical system in the immersion methodis 1.33 times that in the conventional method, the resolving power inthe immersion method improves to 1.33 times that in the conventionalmethod.

In this manner, the immersion method can obtain a resolving powercorresponding to NA≧1, which is impossible in the conventional method.To achieve the immersion method, various exposure apparatuses areproposed.

Japanese Patent Laid-Open No. 2005-19864 proposes an exposure apparatuswhich comprises a liquid supply nozzle arranged around a projectionoptical system in a first direction when seen from it, and a flat plate(top plate) arranged on a substrate stage to be nearly flush with thesurface of a substrate to hold an immersion region. This exposureapparatus supplies a liquid onto the substrate surface via the liquidsupply nozzle when the substrate stage moves the substrate in a seconddirection opposite to the first direction. The liquid is continuouslysupplied onto the substrate surface via the liquid supply nozzle so thata liquid film extends continuously as the substrate moves. This makes itpossible to surely fill the space between the substrate surface and thefinal surface of the projection optical system with the liquid.

Japanese Patent Laid-Open No. 2005-116570 proposes an exposure apparatuswhich comprises a light-receiving unit for receiving light which haspassed though a projection optical system via a slit plate arranged onthe image plane of the projection optical system, and a temperaturesensor for detecting the temperature information of a liquid which fillsthe space between the projection optical system and the slit plate. Thisexposure apparatus irradiates and exposes a substrate arranged on theimage plane side of the projection optical system, with exposure lightvia the projection optical system and liquid. Using the detection resultobtained by the light-receiving unit and the measurement result obtainedby the temperature sensor, this apparatus calculates performanceinformation including the imaging performance. This allows accurateexposure processing by satisfactorily performing exposure stateoptimization processing on the basis of the light-receiving resultobtained by the light-receiving unit.

Japanese Patent Laid-Open No. 2005-191557 proposes an exposure apparatuswhich comprises a substrate table for holding a substrate and a platemember which is exchangeably arranged on the substrate table and has aliquid-repellent flat surface. This makes it possible to prevent theliquid from remaining on the substrate table.

Japanese Patent Laid-Opens No. 2005-19864 disclose a rectangularmeasurement member. The rectangular measurement member rotates relativeto a top plate when being assembled on a substrate stage. Then, thewidth of the gap between the opening side surface of the top plate andthe outer surface of the measurement member readily changes depending onthe gap position. Assume here that a liquid supplied to the spacebetween a projection optical system and a wafer nonuniformly enters thegap. In this case, the temperature drop of the liquid due to itsvaporization heat varies, so the thermal deformation amount of themeasurement member also varies. This may result in a decrease in theaccuracy of measurement using a reference mark.

When a drainage unit for draining the liquid which has entered the gapbetween the opening side surface of the top plate and the outer surfaceof the measurement member is formed in the measurement member, theeasiness of mounting of the drainage unit may be limited.

Japanese Patent Laid-Open No. 2005-19864, No. 2005-116570, and No.2005-191557 does not disclose a concrete structure to prevent a liquidwhich has entered the gap between the opening side surface of the topplate and the outer surface of the measurement member from reaching thesubstrate stage.

SUMMARY OF THE INVENTION

The present invention provides an exposure apparatus which can improvethe accuracy of measurement using a measurement member, and a devicemanufacturing method.

The present invention also provides an exposure apparatus which canimprove the easiness of mounting of a drainage unit, and a devicemanufacturing method.

The present invention also provides an exposure apparatus which canreduce deterioration in constituent elements, and a device manufacturingmethod.

According to the first aspect of the present invention, there isprovided an exposure apparatus which exposes a substrate via a liquid,comprising: a projection optical system configured to project a patternof a reticle onto the substrate; a substrate stage configured to holdthe substrate and move; a top plate which is arranged on the substratestage and in which an opening is formed; and a measurement member whichis arranged in the opening formed in the top plate arranged on thesubstrate stage, wherein a gap is formed between the top plate and themeasurement member in a plane perpendicular to an optical axis of theprojection optical system, and wherein the measurement member is formedof one of a regular N-sided polygon (N>4) and a circle in the plane.

According to the second aspect of the present invention, there isprovided an exposure apparatus which exposes a substrate via a liquid,comprising: a projection optical system configured to project a patternof a reticle onto the substrate; a substrate stage configured to holdthe substrate and move; a top plate which is arranged on the substratestage and in which an opening is formed; and a measurement member whichis arranged in the opening formed in the top plate arranged on thesubstrate stage, wherein a gap is formed between the top plate and themeasurement member in a plane perpendicular to an optical axis of theprojection optical system, and wherein the exposure apparatus satisfiesfollowing formula: γ·cos θ1·L1+γ·cos θ2·L2+Pf·S<0 where θ1 is a contactangle between the measurement member and the liquid, L1 is an outercircumferential length of the measurement member in the plane, θ2 is acontact angle between the top plate and the liquid, L2 is an innercircumferential length of the opening in the plane, Pf is a liquidpressure of the liquid which has partially entered the gap, γ is asurface tension of the liquid, and S is an area of the gap in the plane.

According to the third aspect of the present invention, there isprovided an exposure apparatus which exposes a substrate via a liquid,comprising: a projection optical system configured to project a patternof a reticle onto the substrate; a substrate stage configured to holdthe substrate and move; a top plate which is arranged on the substratestage and in which an opening is formed; and a measurement member whichis arranged in the opening formed in the top plate arranged on thesubstrate stage, wherein a gap is formed between the top plate and themeasurement member in a plane perpendicular to an optical axis of theprojection optical system, and wherein the top plate including adrainage unit configured to drain the liquid which has entered the gap.

According to the fourth aspect of the present invention, there isprovided an exposure apparatus which exposes a substrate via a liquid,comprising: a projection optical system configured to project a patternof a reticle onto the substrate; a substrate stage configured to holdthe substrate and move; a top plate which is arranged on the substratestage and in which an opening is formed; a measurement member which isarranged in the opening formed in the top plate arranged on thesubstrate stage and which has a front surface facing a rear surface ofthe top plate; and a seal member arranged between the rear surface ofthe top plate and the front surface of the measurement member, wherein amodulus of section of the seal member is smaller than a modulus ofsection of a circle.

According to the fifth aspect of the present invention, there isprovided a device manufacturing method comprising: exposing a substrateto light using an exposure apparatus according to first aspect of thepresent invention; and developing the exposed substrate.

The exposure apparatus according to the first aspect or second aspect ofthe present invention can improve the accuracy of measurement using ameasurement member.

The exposure apparatus according to the third aspect of the presentinvention can improve the easiness of mounting of a drainage unit.

The exposure apparatus according to the fourth aspect of the presentinvention can reduce deterioration in constituent elements.

Further features and aspects of the present invention will becomeapparent from the following description of exemplary embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing the arrangement of an exposure apparatusaccording to the first embodiment;

FIG. 2 is a plan view showing the arrangement of a wafer stage, topplate, and substrate reference mark member;

FIG. 3 is an enlarged plan view of a substrate reference mark member FMaccording to the first embodiment of the present invention;

FIG. 4 is an enlarged plan view of a substrate reference mark memberaccording to a comparative example;

FIG. 5 is an enlarged plan view of a substrate reference mark memberaccording to a modification to the first embodiment of the presentinvention;

FIG. 6 is an enlarged plan view of a substrate reference mark memberaccording to the second embodiment of the present invention;

FIG. 7 is an enlarged sectional view taken along a line A-A in FIG. 6;

FIG. 8 is an enlarged sectional view of a portion B in FIG. 7;

FIG. 9 is an enlarged plan view of a substrate reference mark memberaccording to a modification to the second embodiment of the presentinvention;

FIG. 10 is an enlarged sectional view of a substrate reference markmember according to the third embodiment of the present invention;

FIG. 11 is an enlarged sectional view of a substrate reference markmember according to a modification to the third embodiment of thepresent invention; and

FIG. 12 is a flowchart illustrating the overall process of manufacturinga semiconductor device.

DESCRIPTION OF THE EMBODIMENTS

The present invention relates to an exposure apparatus and exposuremethod which transfer the pattern of an reticle onto a substrate coatedwith a photosensitive agent in manufacturing a device such as asemiconductor device or liquid crystal display device and, moreparticularly, to an exposure apparatus and exposure method using animmersion method.

An exposure apparatus 100 according to the first embodiment of thepresent invention will be explained with reference to FIG. 1. FIG. 1 isa view showing the arrangement of the exposure apparatus 100 accordingto the first embodiment.

The exposure apparatus 100 comprises an shaping optical system 2,fly-eye lens 3, condenser lens 4, field stop 5, driving unit 6, movableblind 7, relay lens system 8, reticle stage RST, reference plate SP, andprojection optical system 13. The exposure apparatus 100 also comprisesa wafer stage (substrate stage) WST, top plate P, substrate referencemark member FM, liquid supply nozzle 38, liquid recovery nozzle 39,alignment detection system 16, and controlling system CS.

The shaping optical system 2 is arranged downstream of a light source 1along an optical axis PA. Examples of the light source 1 are excimerlaser light sources such as an F₂ excimer laser, ArF excimer laser, andKrF excimer laser, and a metal vapor laser light source. Other examplesof the light source 1 are a pulse light source such as a harmonic wavegenerator of a YAG laser, and a continuous light source such as acombination of a mercury lamp and elliptic reflecting mirror. Anillumination light beam from the light source 1 is set to have apredetermined diameter by the shaping optical system 2, and supplied tothe downstream side along the optical axis PA.

When a pulse light source is used, exposure is switched on or off bycontrolling power supplied from its power supply. When a continuouslight source is used, exposure is switched on or off by a shutter in theshaping optical system 2. Alternatively, exposure may be switched on oroff by opening or closing the movable blind (variable field stop) 7provided as will be described later.

The fly-eye lens 3 is arranged downstream of the shaping optical system2 along the optical axis PA. The fly-eye lens 3 forms a large number ofsecondary light sources on the basis of the light beam which has enteredfrom the shaping optical system 2.

The condenser lens 4 is arranged downstream of the fly-eye lens 3 alongthe optical axis PA. The condenser lens 4 receives the large number ofsecondary light beams which have entered from the large number ofsecondary light source formed in the vicinity of exit surface of thefly-eye lens 3, and guides them to the downstream side along the opticalaxis PA.

The field stop 5 is arranged downstream of the condenser lens 4 alongthe optical axis PA. The field stop 5 has a rectangular slit-likeopening in which the degree of opening is fixed. The longitudinaldirection of the slit-like opening is, e.g., a direction (Y direction)perpendicular to the sheet surface. The field stop 5 forms a light beamhaving a rectangular slit-like section, and limits the amount of lightguided to the relay lens system 8 via the movable blind 7.

Although the field stop 5 is arranged on the side of the condenser lens4 with respect to the movable blind 7 in this embodiment, it may bearranged on the side of the relay lens system 8 with respect to themovable blind 7.

The driving unit 6 and movable blind 7 are arranged downstream of thefield stop 5 along the optical axis PA.

The movable blind 7 includes a first blade 7A, second blade 7B, thirdblade (not shown), and fourth blade (not shown). The first blade 7A andsecond blade 7B define the dimension of a circuit pattern in thescanning direction (X direction), as will be described later. The thirdblade and fourth blade define the dimension of the circuit pattern inthe non-scanning direction (Y direction) perpendicular to the scanningdirection.

The driving unit 6 includes a first driving unit 6A and second drivingunit 6B. The first driving unit 6A drives the first blade 7A under thecontrol of the controlling system CS. The second driving unit 6B drivesthe second blade 7B under the control of the controlling system CS. Thatis, the controlling system CS independently controls the driving of thefirst blade 7A and second blade 7B. Since the degree of opening of themovable blind 7 can be changed in this way, it is also called a variablefield stop.

The relay lens system 8 is arranged downstream of the driving unit 6 andmovable blind 7 along the optical axis PA. The relay lens system 8 setsthe movable blind 7 to be conjugate with the pattern formation surfaceof a reticle R. That is, the relay lens system 8 refracts the light beamwhich has entered from the movable blind 7, and guides it to the reticleR.

The reticle stage RST is arranged downstream of the relay lens system 8along the optical axis PA. The reticle stage RST holds the reticle R.The position of the reticle stage RST is detected by an interferometer22. On the basis of the detection result obtained by the interferometer22, the controlling system CS controls the driving of the reticle stageRST to align the reticle R. The reticle R is illuminated with the lightbeam which is guided from the relay lens system 8 and in which arectangular slit-like illumination region 21 has a uniform illuminance.Since the relay lens system 8 is a bilateral telecentric optical system,the telecentricity is also maintained in the slit-like illuminationregion 21 on the reticle R.

The reference plate SP is arranged around the reticle stage RST. Anreticle reference mark PM is formed on the reference plate SP. Thereticle reference mark PM is used to calibrate the apparatus.

The projection optical system 13 is arranged downstream of the reticlestage RST along the optical axis PA. The projection optical system 13refracts the light beam which has passed through the reticle R andreference plate SP, and guides it to the downstream side along theoptical axis PA. The projection optical system 13 includes a pluralityof optical elements. Of the plurality of optical elements included inthe projection optical system 13, an optical element on the mostdownstream side (image plane side) will be called a final opticalelement hereinafter. The final optical element is planoconvex lenshaving contact flat surface with liquid.

The wafer stage WST is arranged downstream of the projection opticalsystem 13 along the optical axis PA. The wafer stage WST holds a wafer Wvia a wafer chuck WC. The wafer chuck WC chucks the wafer W by vacuumsuction so that the wafer stage WST holds it. The position of the waferstage WST is detected by an interferometer 23. On the basis of thedetection result obtained by the interferometer 23, the controllingsystem CS controls the driving of the wafer stage WST in six axialdirections (X direction, Y direction, Z direction, θx direction, θydirection, and θz direction) to align the wafer W. The θx, θy, and θzdirections are rotation directions about the X-, Y-, and Z-axes,respectively.

The wafer stage WST includes, e.g., an X-Y stage (not shown) whichundergoes driving control in the X and Y directions, and a Z stage (notshown) which undergoes driving control in the Z direction. The circuitpattern of the slit-like illumination region 21 defined on the reticle Rby the movable blind 7 is imaged and transferred onto the wafer W viathe projection optical system 13 with the light beam guided from theprojection optical system 13.

The top plate P is arranged around the wafer stage WST. The top plate Pis formed to have an upper surface nearly flush with the surface of thewafer W. The top plate P is chucked by vacuum suction by a vacuumchucking mechanism (not shown) built in the wafer stage WST, and is heldby the wafer stage WST.

The substrate reference mark member FM is arranged in an opening formedin the top plate P. The substrate reference mark member FM is used tocalibrate the apparatus and align the reticle R and wafer W.

The liquid supply nozzle 38 is arranged above the wafer W at a positionat which it can supply a liquid to the gap (space) between the wafer Wand the final optical element of the projection optical system 13. Theliquid supply nozzle 38 is connected to a liquid supply pipe (notshown). The liquid supply pipe includes, e.g., a pump, temperaturecontroller, and filter (none of them is shown). For example, a liquidundergoes impurity removal by the filter, is heated to a predeterminedtemperature by the temperature controller, is pressurized at apredetermined pressure by the pump, and is supplied to the liquid supplynozzle 38 via the liquid supply pipe. Note that the liquid supply nozzle38 is opened or closed under the control of the controlling system CS,and supplies a liquid to the gap (space) between the wafer W and theprojection optical system 13 at a predetermined timing and in apredetermined period.

The liquid recovery nozzle 39 is arranged above the wafer W at aposition at which it can recover the liquid from the gap (space) betweenthe wafer W and the final optical element of the projection opticalsystem 13. The liquid recovery nozzle 39 includes, e.g., a liquidrecovery pipe, pump, and gas-liquid separator (none of them is shown).For example, the liquid in the gap (space) between the wafer W and thefinal optical element of the projection optical system 13 is recoveredto the liquid recovery pipe via the liquid recovery nozzle 39. Theliquid recovered to the liquid recovery pipe is pressurized at apredetermined pressure by the pump, and is separated into a gascomponent and liquid component by the gas-liquid separator. The gascomponent is drained to the atmosphere, while the liquid component issupplied to the liquid supply pipe and reused. Note that the liquidrecovery nozzle 39 is opened or closed under the control of thecontrolling system CS, and recovers the liquid from the gap (space)between the wafer W and the final optical element of the projectionoptical system 13.

The alignment detection system 16 is arranged above the wafer W at aposition offset from the optical axis PA. That is, the alignmentdetection system 16 adopts an off-axis scheme. The alignment detectionsystem 16 detects an alignment mark on the wafer W and sends thedetection result to the controlling system CS.

The controlling system CS comprises a main control unit 12, movableblind control unit 11, reticle stage driving unit 10, measurementcontrol unit 17, and wafer stage driving unit 15. The main control unit12 monitors or controls the overall operation of the exposure apparatus100.

For example, the measurement control unit 17 controls the alignmentdetection system 16 to perform alignment detection. Alternatively, themeasurement control unit 17 controls a focus detection system (notshown) to perform focus detection.

For example, the main control unit 12 receives information on theposition of the reticle stage RST from the interferometer 22. On thebasis of the position of the reticle stage RST, the main control unit 12determines the driving amount of the reticle stage RST, and sends it tothe reticle stage driving unit 10. On the basis of the driving amountdetermined by the main control unit 12, the reticle stage driving unit10 controls the driving of the reticle stage RST.

For example, the main control unit 12 receives information on theposition of the wafer stage WST. The main control unit 12 receivesinformation on, e.g., the X, Y, and θz positions of the wafer W from thealignment detection system 16. The main control unit 12 receivesinformation on, e.g., the Z, θz, and θy positions of the wafer W fromthe focus detection system. On the basis of the position of the waferstage WST or wafer W, the main control unit 12 determines the drivingamount of the wafer stage WST, and sends it to the wafer stage drivingunit 15. On the basis of the driving amount determined by the maincontrol unit 12, the wafer stage driving unit 15 controls the driving ofthe wafer stage WST.

For example, the main control unit 12 synchronously scans the reticlestage RST and wafer stage WST in the ±X directions via the reticle stagedriving unit 10 and wafer stage driving unit 15, as described above.That is, in transferring a pattern image on the reticle R onto each shotregion on the wafer W via the projection optical system 13 by exposureusing a scanning exposure scheme, the main control unit 12 scans thereticle R in the ±X directions at an average velocity VR relative to theslit-like illumination region 21 set by the field stop 5. Letting β bethe projection magnification of the projection optical system 13, thewafer W is scanned in the ±X directions at a velocity VW (=β·VR) insynchronism with the scanning of the reticle R. With this operation, acircuit pattern image of the reticle R is sequentially transferred ontoeach shot region on the wafer W.

For example, the main control unit 12 receives information on, e.g., thepositions of the first blade 7A and second blade 7B from a sensor (notshown). On the basis of the positions of the first blade 7A and secondblade 7B, the main control unit 12 determines the driving amounts of thefirst blade 7A and second blade 7B, and sends them to the movable blindcontrol unit 11. On the basis of the driving amounts determined by themain control unit 12, the movable blind control unit 11 controls thedriving of the driving unit 6 (first driving unit 6A and second drivingunit 6B). With this operation, the first blade 7A and second blade 7Bare driven to change the degree of opening of the movable blind 7.

The arrangement of the wafer stage WST, top plate P, and substratereference mark member FM will be explained with reference to FIG. 2.FIG. 2 is a plan view showing the arrangement of the wafer stage WST,top plate P, and substrate reference mark member FM.

The wafer stage WST holds the wafer W via the wafer chuck WC (see FIG.1). The wafer chuck WC chucks the wafer W by vacuum suction so that thewafer stage WST holds it. The wafer chuck WC is arranged near a centerSC of gravity of the wafer stage WST. With this arrangement, the wafer Wis held near the center SC of gravity of the wafer stage WST.

A reflecting mirror 24 for the interferometer 23 is arranged on the sidesurfaces of the wafer stage WST. The reflecting mirror 24 includes anX-axis reflecting mirror 24 a and Y-axis reflecting mirror 24 b. Theinterferometer 23 includes an X-axis interferometer 23 a and Y-axisinterferometer 23 b in correspondence with the mirrors 24 a and 24 b.The X-axis interferometer 23 a faces the X-axis reflecting mirror 24 a.The X-axis interferometer 23 a detects, e.g., the X-coordinate positionof the wafer stage WST by receiving detection light which is projectedby the X-axis interferometer 23 a and reflected by the X-axis reflectingmirror 24 a. The Y-axis interferometer 23 b faces the Y-axis reflectingmirror 24 b. The Y-axis interferometer 23 b detects, e.g., theY-coordinate position of the wafer stage WST by receiving detectionlight which is projected by the Y-axis interferometer 23 b and reflectedby the Y-axis reflecting mirror 24 b.

The top plate P is arranged around the wafer stage WST. For example, onthe wafer stage WST, the top plate P is arranged to fully cover a regionother than a region to hold the wafer W. The top plate P is formed tohave an upper surface nearly flush with the surface of the wafer W. Evenwhen the peripheral region of the wafer W is filled with a liquid, it ispossible to support the liquid in the vicinity of the peripheral regionof the wafer W with the top plate P.

The substrate reference mark member FM is arranged in the opening formedin the top plate P. The substrate reference mark member FM is formed ofa roughly circular shape when seen from above.

A comparison between a substrate reference mark member FMRec accordingto a comparative example and the substrate reference mark member FMaccording to the first embodiment will be explained with reference toFIGS. 3 and 4. FIG. 3 is an enlarged plan view of the substratereference mark member FM according to the first embodiment of thepresent invention. FIG. 4 is an enlarged plan view of the substratereference mark member FMRec according to the comparative example.

Consider, as the comparative example, a case in which a verticallyelongated rectangular substrate reference mark member FMRec is formed onthe top plate P (see FIG. 2), as shown in FIG. 4.

The substrate reference mark member FMRec according to the comparativeexample includes a reference mark main body FMRec1 and gap FMRec2. Thereference mark main body FMRec1 is formed to have an upper surface whichis flush with (which has the same surface level as) that of the topplate P. The gap FMRec2 is recessed with respect to the top plate P andreference mark main body FMRec1, and serves as the gap between theopening side inner surface of the top plate P and the outer surface ofthe reference mark main body FMRec1. With this arrangement, thealignment detection system 16 can detect the shape of the substratereference mark member FMRec by projecting measurement light onto it fromthe Z direction and receiving the light reflected and scattered by it.

The substrate reference mark member FMRec is, after rotation angle ofits mark has been finely tuned, often rotated about a center MC ofgravity in a rotation direction indicated by an arrow relative to thewafer stage WST. In this case, the substrate reference mark member FMRecis rotated relative to the top plate P (accordingly, relative to the X-Ycoordinate system of the interferometer 23 (see FIG. 2) and thereference plate SP or reticle R).

Assume, for example, that the substrate reference mark member FMRec isrotated from a position indicated by a solid line to a positionindicated by a broken line in FIG. 4. In this case, a width WRec1 of afirst portion FMRec21 differs from a width WRec2 of a second portionFMRec22 in the gap FMRec2. Because WRec1<WRec2, when the gap between thesurface of the wafer W and the final optical element of the projectionoptical system 13 is filled with a liquid, the liquid is less likely toenter the first portion FMRec21 but is more likely to enter the secondportion FMRec22. A width URec1 of a third portion FMRec23 differs from awidth URec2 of a fourth portion FMRec24 in the gap FMRec2. BecauseURec1<URec2, when the gap between the surface of the wafer W and thefinal optical element of the projection optical system 13 is filled witha liquid, the liquid is less likely to enter the third portion FMRec23but is more likely to enter the fourth portion FMRec24. When seen fromabove, an area CARec1 of the gap FMRec2 in a first region CRRec1 differsfrom an area CARec2 of the gap FMRec2 in a second region CRRec2. BecauseCARec1<CARec2, when the gap between the surface of the wafer W and thefinal optical element of the projection optical system 13 is filled witha liquid, the liquid is less likely to enter the first region CRRec1 butis more likely to enter the second region CRRec2.

In this manner, the amount of liquid which enters the gap FMRec2 variesdepending on the position in it. When the alignment detection system 16projects measurement light onto the substrate reference mark memberFMRec, its measurement value varies because the amount of liquid whichenters the gap FMRec2 varies. This may result in a decrease in theaccuracy of measurement using the substrate reference mark member FMRec.

Since the amount of liquid which enters the gap FMRec2 varies, thetemperature drop of the liquid due to its vaporization heat also varies,and therefore the thermal deformation amount of the substrate referencemark member FMRec also varies. The measurement value obtained by thealignment detection system 16 varies because the thermal deformationamount of the substrate reference mark member FMRec varies. This mayresult in a decrease in the accuracy of measurement using the substratereference mark member FMRec.

In contrast, the substrate reference mark member FM according to thefirst embodiment of the present invention is formed of a roughlycircular shape, as shown in FIG. 3.

The substrate reference mark member FM according to the first embodimentof the present invention includes a reference mark main body(measurement member) FM1 and gap FM2 in a plane perpendicular to theoptical axis of the projection optical system 13. The reference markmain body FM1 is formed to have an upper surface which is flush with(which has the same surface level as) that of the top plate P. The outersurface of the reference mark main body FM1 faces the inner surface ofthe top plate P at an almost constant distance. The gap FM2 is recessedwith respect to the top plate P and reference mark main body FM1, andserves as the gap between the top plate P and the reference mark mainbody FM1. With this arrangement, the alignment detection system 16 candetect the shape of the substrate reference mark member FM by projectingmeasurement light onto it from the Z direction and receiving the lightreflected and scattered by it.

The substrate reference mark member FM is often rotated about a centerMC of gravity in a rotation direction indicated by an arrow relative tothe wafer stage WST. In this case, the substrate reference mark memberFM is rotated relative to the top plate P (accordingly, relative to theX-Y coordinate system of the interferometer 23 (see FIG. 2) and thereference plate SP or reticle R).

Assume, for example, that the substrate reference mark member FM is,after rotation angle of its mark has been finely tuned, rotated from thestate shown in FIG. 3 through an angle nearly equal to the angle ofrotation from a position indicated by a solid line to a positionindicated by a broken line in FIG. 4. In this case, a width W1 of afirst portion FM21 is nearly equal to a width W2 of a second portionFM22 in the gap FM2. Because W1 W2, when the gap between the surface ofthe wafer W and the final optical element of the projection opticalsystem 13 is filled with a liquid, the liquid uniformly enters the firstportion FM21 and second portion FM22. A width U1 of a third portion FM23is nearly equal to a width U2 of a fourth portion FM24 in the gap FM2.Because U1≈U2, when the gap between the surface of the wafer W and thefinal optical element of the projection optical system 13 is filled witha liquid, the liquid uniformly enters the third portion FM23 and fourthportion FM24. When seen from above, an area CA1 of the gap FM2 in afirst region CR1 is nearly equal to an area CA2 of the gap FM2 in asecond region CR2. Because CA1≈CA2, when the gap between the surface ofthe wafer W and the final optical element of the projection opticalsystem 13 is filled with a liquid, the liquid uniformly enters the firstregion CR1 and second region CR2.

In this manner, the amount of liquid which enters the gap FM2 hardlyvaries depending on the position in it. That is, when the alignmentdetection system 16 projects measurement light onto the substratereference mark member FM, its measurement value hardly varies becausethe amount of liquid which enters the gap FM2 hardly varies. This makesit possible to improve the accuracy of measurement (e.g., alignmentmeasurement and calibration measurement) using the substrate referencemark member FM.

Since the amount of liquid which enters the gap FM2 hardly varies, thetemperature drop of the liquid due to its vaporization heat also hardlyvaries, and therefore the thermal deformation amount of the substratereference mark member FM also hardly varies. The measurement valueobtained by the alignment detection system 16 hardly varies because thethermal deformation amount of the substrate reference mark member FMhardly varies. This makes it possible to improve the accuracy ofmeasurement using the substrate reference mark member FM.

The arrows shown in FIGS. 3 and 4 do not limit the rotation directions.The same applies to a case in which the reference mark main body FM1 ofthe substrate reference mark member FM is rotated in an oppositerotation direction relative to the wafer stage WST.

The substrate reference mark member may be formed of a shape other thana roughly circular shape. For example, a substrate reference mark memberFMHe may be formed of a roughly regular hexagonal shape, as shown inFIG. 5. Alternatively, the substrate reference mark member may be formedof a regular N-sided polygon (N>4). Even in this case, the width of thegap of the substrate reference mark member FM hardly varies. With thisarrangement, the alignment detection system 16 can improve the accuracyof measurement using the substrate reference mark member as comparedwith a case in which the substrate reference mark member FMRec is formedof a rectangle.

A plurality of substrate reference members may be formed on the waferstage WST.

An exposure apparatus 200 according to the second embodiment of thepresent invention will be explained next with reference to FIGS. 6 to 8.FIG. 6 is an enlarged plan view of a substrate reference mark memberFM200 according to the second embodiment of the present invention. FIG.7 is an enlarged sectional view taken along a line A-A. FIG. 8 is anenlarged sectional view of a portion B in FIG. 7. Parts different fromthose in the first embodiment will be mainly described below, and adescription of the same parts will not be made.

The exposure apparatus 200 has the same basic arrangement as that in thefirst embodiment, but is different from the first embodiment in thearrangement of the substrate reference mark member FM200.

The substrate reference mark member FM200 is formed of a roughlycircular shape as in the first embodiment, but is different from thefirst embodiment in its detailed arrangement.

That is, as shown in FIG. 6, the substrate reference mark member FM200satisfies:

S=π·g·(D+g)  (1)

L1=π·D  (2)

L2=π·(D+2·g)  (3)

where D is the diameter of a reference mark main body FM201, L1 is theouter circumferential length of the reference mark main body FM201, g isthe (average) width of a gap FM202, L2 is the outer circumferentiallength (the inner circumferential length of an opening of a top plate P)of the gap FM202, and S is the area of the gap FM202 when seen fromabove.

As shown in FIGS. 7 and 8, the gap FM202 of the substrate reference markmember FM200 is formed to have a width g at which a liquid 35 betweenthe surface of a wafer W and a final optical element of a projectionoptical system 13 does not fully enter the gap FM202. That is, theliquid 35 is divided into a first liquid portion 35 a on the substratereference mark member FM200 and a second liquid portion 35 b which haspartially entered the gap FM202. Let θ1 be the contact angle at whichthe reference mark main body FM201 of the substrate reference markmember FM200 is in contact with the second liquid portion 35 b. Let θ2be the contact angle at which the top plate P is in contact with thesecond liquid portion 35 b. Let γ be the surface tension of the secondliquid portion 35 b. Let Fw1 and Fw2 be permeation forces generated bythe surface tension γ of the second liquid portion 35 b. Let Pf be theliquid pressure around the surface of the second liquid portion 35 b.Then, to prevent the second liquid portion 35 b from entering the gapFM202 (except a partial region), the gap FM202 is formed to have an areaS which satisfies:

Fw1+Fw2+Pf·S<0  (4)

Fw1+Fw2+Pf/S<0  (5)

Fw1=γ·cos θ1·L1  (6)

Fw2=γ·cos θ2·L2  (7)

That is, in accordance with equations (1) to (7), the gap FM202 isformed to have a width g which satisfies:

γ·cos θ1·π·D+γ·cos θ2·π·(D+2·g)+Pf·π·g·(D+g)<0  (8)

Assume, for example, that the diameter of the reference mark main bodyFM201 is D=50 mm, the contact angle between the reference mark main bodyFM201 and the second liquid portion 35 b is θ1=110°, and the contactangle between the top plate P and the second liquid portion 35 b isθ2=110°. The liquid pressure around the surface of the second liquidportion 35 b is Pf=50 Pa, and the surface tension of the second liquidportion 35 b is γ=0.0728 N/m. The surfaces of the reference mark mainbody FM201 and top plate P, which face the liquid 35, have undergone aliquid-repellent treatment. The liquid 35 is 100% pure water.Substituting these numerical values for equation (8) reveals that thegap FM202 is formed to have a width g less than 0.996 mm.

In this manner, the gap FM202 of the substrate reference mark memberFM200 is formed to have a width g at which the liquid 35 does not enterthe gap FM202 (except a partial region). This makes it possible toprevent the liquid 35 from entering a relatively lower portion of thegap FM202. It is therefore possible to prevent any defect (e.g., rust)generated as the liquid enters the gap.

The substrate reference mark member may be formed of a regular N-sidedpolygon (N>4) in place of a roughly circular shape. Alternatively, forexample, a reference mark main body FM201 i of a substrate referencemark member FM200 i in an exposure apparatus 200 i according to amodification may be formed of a roughly square shape with circularcorners when seen from above, as shown in FIG. 9.

That is, as shown in FIG. 9, the substrate reference mark member FM200 isatisfies:

S=π·((R+g)·2−R·2)+2·X·g+2·γ·g  (9)

L1=2π·R+4·X  (10)

L2=2π·(R+g)+4·X  (11)

where Xi is the length of a linear portion of the reference mark mainbody FM201 i, R is the radius of curvature of a curved portion of thereference mark main body FM201 i, L1 i is the outer circumferentiallength of the reference mark main body FM201 i, gi is the (average)width of a gap FM202 i, L2 i is the outer circumferential length of thegap FM202 i, and Si is the area of the gap FM202 i when seen from above.

The gap FM202 i is formed to satisfy equations (4) to (7), as in thesecond embodiment. That is, in accordance with equations (4) to (11),the gap FM202 is formed to have a width g which satisfies:

Pf·π·g·2+((2·Pf·(2·X+π·R)+2·π·γ·cos θ2)·g+(γ·cos θ1+γ·cosθ2)·(4·X+2·π·R)<0  (12)

If the mark main body of the substrate reference mark member is formedof a regular N-sided polygon (N>4) with circular corners when seen fromabove, the gap is formed to have a width g which satisfies:

Pf·π·(1−n/2)·g·2+(2·π·(1−n/2)·(γ·cosθ2+Pf·R)+Pf·n·X)·g+γ·(n·X+2·π·R(1−n/2))·(cos θ1+cos θ2)<0  (13)

An exposure apparatus 300 according to the third embodiment of thepresent invention will be explained next with reference to FIG. 10. FIG.10 is an enlarged sectional view of a substrate reference mark memberFM300 according to the third embodiment of the present invention.

The exposure apparatus 300 has the same basic arrangement as that in thefirst embodiment, but is different from the first embodiment in thearrangement of the substrate reference mark member FM300.

The substrate reference mark member FM300 is formed of a roughlycircular shape as in the first embodiment, but is different from thefirst embodiment in its detailed arrangement.

That is, the substrate reference mark member FM300 comprises a bolt (notshown), reference mark main body FM301, photoelectric conversion device36, optical element 37, gap FM302, drainage unit 32, and seal member 31.

The bolt fixes the reference mark main body FM301 on a wafer stage WST.

The reference mark main body FM301 includes a glass portion 30 andsupporting portion 33. The glass portion 30 is formed fromlight-transmittable glass and located at the upper portion of thereference mark main body FM301. A mark for apparatus calibration oralignment is drawn on the glass portion 30. The supporting portion 33supports the glass portion 30 on the wafer stage WST.

The photoelectric conversion device 36 is formed to be covered with thereference mark main body FM301. With this arrangement, the photoelectricconversion device 36 can receive detection light scattered by the markat the upper portion (glass) of the reference mark main body FM301.

The optical element 37 is formed of a hemisphere and arranged betweenthe glass portion 30 and the photoelectric conversion device 36 whilebeing held by optical contact. When detection light with NA≧1 is appliedto the glass portion 30 via a liquid 35, the optical element 37 canguide the light to the photoelectric conversion device 36 without totalreflection. In this embodiment, the detection light may be the exposurelight.

The gap FM302 is recessed with respect to a top plate P and thereference mark main body FM301, and serves as the gap between an openingside inner surface Pa of the top plate P and an outer surface 33 a ofthe reference mark main body FM301. The inner surface Pa includes avertical surface Pa1, horizontal surface Pa2, and vertical surface Pa3.The outer surface 33 a includes a vertical surface 33 a 1, horizontalsurface (front surface) 33 a 2, and vertical surface 33 a 3.

The drainage unit 32 is formed to surround the reference mark main bodyFM301 below the gap FM302. The drainage unit 32 is connected to adrainage pipe (not shown). The drainage pipe has a drainage pump (notshown) to generate a negative pressure in the drainage pipe, therebyfacilitating drainage. The drainage unit 32 is formed from a porousmaterial, and its porosity is adjusted so as to reduce a variation indrainage velocity (or drainage flow rate) throughout the entirecircumference. The drainage pump can modulate the drainage velocity (ordrainage flow rate) in the drainage pipe under the control of thecontrolling system CS. This makes it possible to reduce a variation inthe drainage velocity (or drainage flow rate) of liquid 35 flowing intothe drainage unit 32 via the gap FM302.

The seal member 31 is arranged in the gap formed between the horizontalsurface (rear surface) Pa2 in the opening side inner surface Pa of thetop plate P and the horizontal surface 33 a 2 in the outer surface 33 aof the reference mark main body FM301. The seal member 31 supports thetop plate P from below. The modulus of section of the seal member 31 issmaller than the modulus of section of a circle. An example of the sealmember 31 is a lip seal formed from, e.g., high-purity fluorocarbonrubber.

The seal member 31 is arranged on the outer circumferential side(outside the center MC of gravity of the reference mark main body FM301in the radial direction) of the drainage unit 32. The seal member 31seals the gap formed between the horizontal surface Pa2 in the openingside inner surface Pa of the top plate P and the horizontal surface 33 a2 in the outer surface 33 a of the reference mark main body FM301.

Consider a case in which the liquid 35 has entered the gap FM302 of thesubstrate reference mark member FM300. Most of the liquid 35 which hasentered the gap FM302 is drained by the drainage unit 32. The drainageunit 32 is adjusted so as to reduce a variation in the drainage velocity(or drainage flow rate) throughout the entire circumference byutilizing, e.g., its material characteristics and the drainage pump onits downstream side. With this arrangement, the amount of liquid flowingthrough the gap FM302 hardly varies. This makes it possible to improvethe accuracy of measurement using the substrate reference mark memberFM300.

Since the amount of liquid flowing through the gap FM302 hardly varies,the temperature drop of the liquid due to its vaporization heat alsohardly varies, and therefore the thermal deformation amount of thesubstrate reference mark member FM300 also hardly varies. This makes itpossible to improve the accuracy of measurement using the substratereference mark member FM300.

Since the drainage unit 32 is formed near the lower surface of the topplate P, it is possible to suppress the drainage unit 32 from beingirradiated with exposure light. Even when the drainage unit 32 is madeof a porous material, it hardly suffers contamination.

The liquid 35 which has reached the outer circumference of the drainageunit 32 without being drained from the drainage unit 32 is preventedfrom moving to the wafer stage WST by the seal member 31. That is, thegap FM302 and wafer stage WST form a spatially, nearly sealed structurebetween themselves. This makes it possible to suppress the liquid 35from scattering to the wafer stage WST. It is therefore possible tosuppress, e.g., the wafer stage WST from suffering any defect such asrust, thus reducing deterioration in the constituent elements of theexposure apparatus 300.

Since the modulus of section of the seal member (e.g., a lip seal) 31 issmaller than that of a circle, its rigidity can be decreased as comparedwith a case in which the seal member is, e.g., an O-ring. This makes itpossible to reduce a reaction force which the seal member applies to thetop plate P upon sealing the gap. The top plate P can thus be suppressedfrom floating upon canceling the vacuum chucking force acting on it. Itis therefore possible to suppress, e.g., the top plate P from clashingwith a projection optical system 13, liquid supply nozzle 38, and liquidrecovery nozzle 39 and damaging them, thus reducing deterioration in theconstituent elements of the exposure apparatus 300.

Assume, for example, that the inner diameter of the seal member is about70 mm. If the seal member is an O-ring, its reaction force is about 20kgf. In contrast, if the seal member is a lip seal, its reaction forcecan be suppressed to about 2 kgf.

Since a reaction force which the seal member applies to the top plate Pupon sealing the gap can be reduced, it is possible to decrease therigidity required for the supporting portion 33 of the reference markmain body FM301 and that required for the top plate P supported by theseal member 31. This makes it possible to decrease the thickness of thesupporting portion 33 of the reference mark main body FM301 and that ofthe top plate P, thus reducing the weights of the reference mark mainbody FM301 and top plate P.

As the top plate P is arranged on the wafer stage WST, it preferably hasa light weight and high rigidity. The top plate P is preferably formedfrom, e.g., ceramics. A reaction force which the seal member 31 appliesto the top plate P is preferably equal to or smaller than the gravityacting on the top plate P. Assume that a reaction force which the sealmember 31 applies to the top plate P is equal to or larger than thegravity acting on the top plate P. In this case, upon turning off avacuum chucking mechanism (not shown) chucking the top plate P by vacuumsuction, the top plate P floats due to a reaction force which the sealmember 31 applies to the top plate P. Consequently, the upper surface ofthe top plate P becomes higher than the surface of a wafer W. In thisstate, when the wafer stage WST moves, the top plate P may clash with,e.g., the projection optical system 13, liquid supply nozzle 38, andliquid recovery nozzle 39.

As shown in FIG. 11, a drainage unit 32 i for draining the liquid 35which has entered the gap FM302 in an exposure apparatus 300 i may beformed by opening the top plate P. Arranging the drainage unit 32 i onthe top plate P makes it possible to freely extend a drainage pipe (notshown) connected to the drainage unit 32 i inside the top plate P. Thismakes it possible to improve the degree of freedom of design (theeasiness of mounting) of each of the drainage unit 32 i and drainagepipe. When a plurality of substrate reference mark members FM300 areformed on the wafer stage WST, it is possible to branch and integratedrainage pipes for the plurality of substrate reference mark membersFM300 inside the top plate P, thus improving the easiness of mounting aswell. Although FIG. 11 shows an example in which the drainage unit 32 iis arranged on the vertical surface Pa1 in the opening side innersurface Pa of the top plate P, it may be arranged on the horizontalsurface Pa2 in the opening side inner surface Pa of the top plate P.This makes it possible to suppress the drainage unit 32 from beingirradiated with exposure light and hence to irradiate a porous portionwith the exposure light. It is therefore possible to reducedeterioration in the constituent elements so as to prevent contaminationgeneration.

A reference mark formed on the upper surface of a reference mark mainbody of a substrate reference mark member according to each of the firstto third embodiments may have a slit shape as disclosed in, e.g.,Japanese Patent Laid-Open No. 2005-175034 (U.S. Pat. No. 7,221,431).

For example, a measurement unit which performs measurement using areference mark main body of a substrate reference mark member mayinclude, e.g., an illuminance sensor disclosed in Japanese PatentLaid-Open No. 11-16816 (US Application No. 2002/061469). The measurementunit may include, e.g., a wavefront aberration measurement unitdisclosed in Japanese Patent Laid-Open No. 8-22951 (U.S. Pat. No.5,760,879). Note that if the measurement unit includes, e.g., thewavefront aberration measurement unit disclosed in Japanese PatentLaid-Open No. 8-22951, it is necessary to form a glass portion on whicha slit pattern is drawn at the upper portion of the reference mark mainbody so as to prevent a liquid from entering, e.g., the wavefrontaberration measurement unit.

Although each of the first to third embodiments has exemplified ascanning exposure apparatus, the present invention is not particularlylimited to this and may be applied to a step & repeat exposureapparatus. The exposure apparatus may have one or a plurality of waferstages.

A process (method) of manufacturing a device using an exemplary exposureapparatus to which a wafer stage apparatus according to the presentinvention is applied will be explained next with reference to FIG. 12.FIG. 12 is a flowchart illustrating the overall process of manufacturinga semiconductor device as an example of the device.

In step S91 (circuit design), the circuit of a semiconductor device isdesigned.

In step S92 (reticle fabrication), a reticle (also called a mask) isfabricated on the basis of the designed circuit pattern.

In step S93 (wafer manufacture), a wafer (also called a substrate) ismanufactured using a material such as silicon.

In step S94 (wafer process) called a preprocess, the above-describedexposure apparatus forms an actual circuit on the wafer by lithographyusing the reticle and wafer.

In step S95 (assembly) called a post-process, a semiconductor chip isformed using the wafer manufactured in step S94. This step includesprocesses such as assembly (dicing and bonding) and packaging (chipencapsulation).

In step S96 (inspection), inspections including operation check test anddurability test of the semiconductor device manufactured in step S95 areperformed. A semiconductor device is completed with these processes andshipped in step S97.

The wafer process in step S94 includes: an oxidation step of oxidizingthe wafer surface; a CVD step of forming an insulating film on the wafersurface; an electrode formation step of forming an electrode on thewafer by vapor deposition; an ion implantation step of implanting ionsin the wafer; a resist processing step of applying a photosensitiveagent on the wafer; an exposure step of exposing, using theabove-described exposure apparatus, the wafer having undergone theresist processing step to light via the reticle pattern to form a latentimage pattern on the resist; a development step of developing the waferexposed in the exposure step; an etching step of etching portions otherthan the latent image pattern developed in the development step; and aresist removal step of removing any unnecessary resist remaining afteretching. These steps are repeated to form multiple circuit patterns onthe wafer.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

1. An exposure apparatus which exposes a substrate via a liquid,comprising: a projection optical system configured to project a patternof a reticle onto the substrate; a substrate stage configured to holdthe substrate and move; a top plate which is arranged on the substratestage and in which an opening is formed; and a measurement member whichis arranged in the opening formed in the top plate arranged on thesubstrate stage, wherein a gap is formed between the top plate and themeasurement member in a plane perpendicular to an optical axis of theprojection optical system, and wherein the measurement member is formedof one of a regular N-sided polygon (N>4) and a circle in the plane. 2.An exposure apparatus which exposes a substrate via a liquid,comprising: a projection optical system configured to project a patternof a reticle onto the substrate; a substrate stage configured to holdthe substrate and move; a top plate which is arranged on the substratestage and in which an opening is formed; and a measurement member whichis arranged in the opening formed in the top plate arranged on thesubstrate stage, wherein a gap is formed between the top plate and themeasurement member in a plane perpendicular to an optical axis of theprojection optical system, and wherein the top plate including adrainage unit configured to drain the liquid which has entered the gap.3. The apparatus according to claim 2, wherein the drainage unit isadjusted at a constant drainage velocity.
 4. An exposure apparatus whichexposes a substrate via a liquid, comprising: a projection opticalsystem configured to project a pattern of a reticle onto the substrate;a substrate stage configured to hold the substrate and move; a top platewhich is arranged on the substrate stage and in which an opening isformed; a measurement member which is arranged in the opening formed inthe top plate arranged on the substrate stage and which has a frontsurface facing a rear surface of the top plate; and a seal memberarranged between the rear surface of the top plate and the front surfaceof the measurement member, wherein a modulus of section of the sealmember is smaller than a modulus of section of a circle.
 5. Theapparatus according to claim 5, wherein the seal member includes a lipseal.
 6. A device manufacturing method comprising: exposing a substrateto light using an exposure apparatus defined in claim 1; and developingthe exposed substrate.
 7. A device manufacturing method comprising:exposing a substrate to light using an exposure apparatus defined inclaim 2; and developing the exposed substrate.
 8. A device manufacturingmethod comprising: exposing a substrate to light using an exposureapparatus defined in claim 4; and developing the exposed substrate.